Anti-Spouse is a a word used to describe heterosexual couples who choose not to marry based upon their own personal beliefs that there is no need to muck up a good friendship with a marital contract, and choose to live as though married (ie: together and monogamous) but are not recognized as common law.
Living together and monogamously is precisely what common law recognises (at least in Australia) hence de facto couples are treated by the courts and in administrative processes in the same fashion as those who are legally married.
It's a wee bit different here in the States. You must live together for a period of 7 years to be considered common law..and even then individuals are treated as just that. Individuals. While you may share a residence and property, you still haven't bonded yourself to our government through the vows to a God you may not even believe in.
The number of years depends on the state, as do the rights appertaining to common law status. But on the whole, it's true that common law couples might not be granted the legal rights of spouses in most states. Civil unions, however, grant all legal rights of a married couple without the involvement of any god.